The present invention relates generally to a hydraulic system and, more specifically, to a control valve assembly of a hydraulic system that selectively engages regeneration.
It is typical on digging machines such as backhoes and excavators to transfer earth into the bucket during the ‘dig’ segment of the cycle. During this cycle the operator will command the arm (aka dipper, crowd) cylinder to extend (arm in), bucket cylinder to extend (bucket curl) and boom cylinder to extend (boom up). During this action all three of the cylinders will extend and fill the bucket under the operators command. The pressures in the cylinders are typically not the same and the pressure difference between the pump and the cylinders is throttled by either a primary spool valve that the operator is commanding or a pressure compensator. These throttling losses create hydraulic heat and have a negative effect on machine efficiency. It is typical on these machines to have power efficiencies from pump outlet to the cylinders in the mid-60% range during the digging operation segments. One of the key sources of hydraulic heat and inefficiency is the gap between the high pressure load in the arm during digging which sets the pump pressure and the relatively low pressure load in the boom. If the operator is not commanding boom during the cycle there are no losses to the boom. In some duty cycles, almost half of the total losses during the dig are from the unequal pressure between the boom and pump caused by the high arm load. Due to the other dig segments and varied use of the machine, the boom cylinders cannot be redesigned to mitigate this pressure difference.
Accordingly, there remains a considerable need for hydraulic control valve systems that can improve the efficiency of the operation to overcome these shortcomings.